Pure substances can or can not be chemically combined.
Pure substances can be either elements or compounds, but not mixture. Mixture are different substances mixing together without being chemically combined, such as air, which is a mixture of oxygen, carbon dioxide, water etc. Mixture can be separated by physical methods, like filtration or decantation.
Meanwhile, elements are the substances that cannot be further separated by any means. No matter physical or chemical methods. Examples of elements are oxygen, hydrogen, neon and all the other ones from the periodic table. Compounds are basically elements joining together, but they’re chemically combined which means their electrons (kind of subatomic particle) are either shared or given away. These elements can only be separated by chemical methods like electrolysis or heating.
Therefore, as long as the substance cannot be separated by physical methods, it can be considered as a pure substance. We can now conclude that pure substance can be (element) or can not be (compound) chemically combined.
Answer:
The element is CARBON
The number 6 refers to the ATOMIC NUMBER
the numbers 12, 13, and 14 refer to the ATOMIC MASS
how many protons and neutrons are in the first isotope?
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how many protons and neutrons are in the second isotope?
<u>6</u><u>. </u><u> </u><u> </u><u> </u><u> </u><u> </u><u>7</u>
<u>how many protons and neutrons are in the </u><u>t</u><u>h</u><u>i</u><u>r</u><u>d</u><u> </u><u>isotope?</u>
<u>6</u><u>. </u><u> </u><u> </u><u> </u><u> </u><u> </u><u> </u><u>8</u>
<u>y</u><u>o</u><u>u</u><u> </u><u>a</u><u>r</u><u>e</u><u> </u><u>w</u><u>e</u><u>l</u><u>c</u><u>o</u><u>m</u><u>e</u><u> </u><u>:</u><u>)</u>
Answer: 2. cannot be an element.
Explanation:
Element is a pure substance which is composed of atoms of similar elements.It can not be decomposed into simpler constituents using chemical reactions.Example: Copper 
Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.It can be decomposed into simpler constituents using chemical reactions. Example: methane 

Thus as it can be decomposed into its constituent elements, it is a compound.
Mixture is a substance which has two or more components which do not combine chemically and do not have any fixed ratio in which they are present.
Thus methane cannot be an element.
Answer:
Explanation:
Convergent boundaries: where two plates are colliding. Subduction zones occur when one or both of the tectonic plates are composed of oceanic crust. ...
Divergent boundaries – where two plates are moving apart. ...
Transform boundaries – where plates slide passed each other.
Answer:
The answer is "0.00172172603".
Explanation:
Given:

Formula:

